The Fiat AS.5 was an Italian 12-cylinder, liquid-cooled

V engine A V engine, sometimes called a Vee engine, is a common configuration for internal combustion engines. It consists of two cylinder banks—usually with the same number of cylinders in each bank—connected to a common crankshaft. These cylinder ...

designed and built in the late-1920s by

Fiat Fiat Automobiles S.p.A. (, , ; originally FIAT, it, Fabbrica Italiana Automobili di Torino, lit=Italian Automobiles Factory of Turin) is an Italian automobile manufacturer, formerly part of Fiat Chrysler Automobiles, and since 2021 a subsidiary ...

especially for the 1929

Schneider Trophy The Coupe d'Aviation Maritime Jacques Schneider, also known as the Schneider Trophy, Schneider Prize or (incorrectly) the Schneider Cup is a trophy that was awarded annually (and later, biennially) to the winner of a race for seaplanes and flying ...

air race.Gunston 1989, p. 57.

Design and development

For the 1929 Schneider Trophy contest Fiat planned a new

seaplane A seaplane is a powered fixed-wing aircraft capable of takeoff, taking off and water landing, landing (alighting) on water.Gunston, "The Cambridge Aerospace Dictionary", 2009. Seaplanes are usually divided into two categories based on their tec ...

to counter the British challengers from

Gloster Gloster may refer to: People with the surname * Elizabeth Gloster (born 1949), English judge * J. Gary Gloster (born 1936), American bishop in The Episcopal Church * John Gloster (born before 1998), Australian physiotherapist who works with crick ...

and

Supermarine Supermarine was a British aircraft manufacturer that is most famous for producing the Spitfire fighter plane during World War II as well as a range of seaplanes and flying boats, and a series of jet-powered fighter aircraft after World War II. ...

. To minimise frontal area they chose a compact V-12 engine design that set new size standards for a 1,000-horsepower (750 kW) class engine. This unsupercharged engine had a high

power-to-weight ratio Power-to-weight ratio (PWR, also called specific power, or power-to-mass ratio) is a calculation commonly applied to engines and mobile power sources to enable the comparison of one unit or design to another. Power-to-weight ratio is a measuremen ...

due to the use of a high

compression ratio The compression ratio is the ratio between the volume of the cylinder and combustion chamber in an internal combustion engine at their maximum and minimum values. A fundamental specification for such engines, it is measured two ways: the stat ...

and a special fuel blend containing a 50/50 mix of

petrol Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organic c ...

and

benzole In the United Kingdom, benzole or benzol is a coal-tar product consisting mainly of benzene and toluene. It was originally used as a 'motor spirit', as was petroleum spirits. Benzole was also blended with petrol and sold as a motor fuel under tra ...

. A problem encountered with the AS.5 was that it developed maximum power at high crankshaft speeds (3,000 rpm) but lacked output gearing, so that great care had to be taken with the choice of propellers. The production version did feature a reduction gear.Eves 2001, p. 217. The AS.5 was developed into the AS.6, essentially a tandem-coupled combination of two AS.5 units.

Applications

Fiat C.29 The Fiat C.29 was an Italian racing seaplane designed by Celestino Rosatelli and built in the late-1920s by Fiat Aviazione especially for the 1929 Schneider Trophy air race. Unused in the race, of the three aircraft built, two were destroyed in ...

Specifications (AS.5)

References

Notes

Bibliography